CII FAQs: Your Questions About Carbon Intensity Indicator Answered

CII is an operational carbon intensity measure mandated under MARPOL Annex VI Regulation 28. It applies to ships of 5,000 gross tonnage and above engaged in international voyages, covering vessel types including bulk carriers, tankers, container ships, gas carriers, general cargo ships, refrigerated cargo carriers, combination carriers, LNG carriers, ro-ro cargo ships, ro-ro passenger ships, and cruise passenger ships.

The Attained CII is calculated as CO2 emissions divided by transport work. For most vessel types this is expressed as the Annual Efficiency Ratio (AER) in grams of CO2 per DWT-nautical mile. The Attained CII is then compared against the Required CII for that vessel type and size, producing a rating of A, B, C, D, or E. The Required CII reduces by 2% per year through 2026, making it progressively harder to maintain the same rating year over year.

A vessel receiving a D rating for three consecutive years, or an E rating in any single year, must develop a corrective action plan as part of its SEEMP Part III. This plan must be approved by the flag state administration and must set out specific measures the operator will implement to improve CII performance in subsequent years. While CII currently does not directly trigger port state control detentions, this is under review at the IMO and may change.

Yes. MEPC has approved correction factors for a range of operational circumstances, including ice-class vessels operating in ice conditions, ship-to-ship transfer operations, and vessels with certain design characteristics. The correction factors are applied to reduce the measured CO2 or transport work, reflecting the additional fuel consumption demands of specific operational contexts. Correctly applying all relevant correction factors is essential for an accurate CII calculation.

Absolutely. Operational measures including speed reduction, weather routing, hull and propeller cleaning, trim optimisation, and auxiliary machinery management can all significantly improve a vessel's Attained CII. For many vessels, operational improvements alone are sufficient to move from a D or E rating to a C rating or above, particularly in the first years of the regime when the Required CII thresholds are relatively accessible.

Every vessel subject to CII must have a SEEMP Part III that documents the vessel's CII management plan. Part III must include the required CII for each year of the current plan period, the vessel's CII goals for each year, a description of the measures to be implemented to achieve those goals, an implementation plan, and a self-evaluation procedure. SEEMP Part III must be developed before the start of the first reporting year and updated annually.

CII is increasingly influencing charter markets. Charterers, particularly those with decarbonization commitments or ESG mandates, are increasingly including CII clauses in time charters. These clauses may specify minimum acceptable CII ratings, assign responsibility for CII-related costs between owner and charterer, or give charterers the right to direct speed and routing decisions to protect the vessel's CII performance. Understanding your vessel's CII implications is now a commercial as well as a technical necessity.

The current CII framework runs through 2026. The IMO has committed to reviewing the CII framework, including the annual reduction rate, the correction factors, and potentially the rating bands themselves, before 2026. Depending on progress against the IMO's updated GHG strategy (which targets net-zero emissions around 2050 and 5% alternative fuels by 2030), the annual reduction factor could increase significantly. Fleet managers should plan for a more stringent CII environment beyond 2026.

Ecosail's CII module automates data collection, calculates Attained CII in real time, generates SEEMP Part III documentation, and provides simulation tools to model operational scenarios. Our regulatory experts monitor MEPC developments and update the platform continuously, ensuring that your CII management is always based on the current methodology. Contact Ecosail today to schedule a demo and see how our CII solution can protect your fleet's ratings and commercial performance.